In seismic modeling, specifically, creating a velocity model of a subterranean domain, estimation of anisotropic parameters provides information useful for characterizing reservoirs, fractures, and fluids in reservoirs. For example, anisotropic models may be built in vertically transversely isotropic (VTI) and tilted transversely isotropic (TTI) media
Recently, some wide-azimuth surveys have become available. Using seismic data from these surveys, anisotropic models of lower symmetry such as orthorhombic and monoclinic may be built. However, estimating orthorhombic anisotropic parameters in laterally varying media is still a challenge. In case of layered media, orthorhombic parameters may be estimated using a local one-dimensional, Dix-like inversion after performing depth migration. A generalized Dix inversion may be employed to characterize the normal moveout (NMO) ellipse using offset gathers.
Structurally transverse isotropic (STI) models may be built using multi-azimuth TTI tomography. Ellipses may then be fit to the estimated transversely isotropic anisotropic parameters to obtain anisotropic parameters defining orthorhombic anisotropy. Elliptical fitting, however, may be sensitive to the resolution of azimuthal sectors used in this type of workflow and in some cases resolution requirements may imply high costs with respect to user or compute time.